Internal combustion engine fuel supply apparatus

ABSTRACT

A system for supplying a substantially uniform combustible fuel mixture for an internal combustion engine includes a compressed air supply line and a compressed fuel gas supply line, each having a first end connected to its respective pressurized supply, a metering orifice portion, and a second end connected to an appropriate part of the engine. At least one of the metering orifice portions is adjustable for establishing various desired air-to-fuel ratios for delivery to the combustion cylinder. The system includes a pressure regulating apparatus in at least one of the lines, between its first end and its metering orifice portion for maintaining substantially equal pressures at all times in the respective supply lines immediately upstream of their respective metering portions. The respective supply line pressures immediately downstream of the metering orifices are also kept substantially equal by connection of both supply lines to a common conduit or mixing chamber. Preferably a pressure regulating valve of the air-loaded or dome-loaded type, which has a controlling pressure chamber and operates in response to changes in fluid pressure in such control chamber, is located in one line and has its control chamber connected to a sensing means so the chamber pressure has a predetermined relationship at all times to the pressure in the other supply line. A temperature control device may also be used in one or both lines to prevent undesired variations in air or fuel gas temperatures which could adversely affect the uniformity of the combustible mixture at different times during operation.

United States Patent Braun 1541 INTERNAL COMBUSTION ENGINE FUEL SUPPLY APPARATUS [76] Inventor: Anton Braun, 6421 Warren Ave.,

Minneapolis, Minn. 55435 [22] Filed: Nov. 12, 1971 [21] Appl. N0.: 198,165

[52] U.S. Cl. ..123/46 R, 123/120, 123/179 G, 60/16 [51] Int. Cl. ..F02b 13/06, F02n 7/00 [58] FieldofSearch ..l23/120,l79G,46R;60/l6 [56] References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS 513,392 10/1939 Great Britain ..123/179 G Primary Examiner-Wendell E. Burns Attorney-Frederick E. Lange et al.

[57] ABSTRACT A system for supplying a substantially uniform com- 145] Mar. 27, 1973 bustible fuel mixture for an internal combustion engine includes a compressed air supply line and a compressed fuel gas supply line, each having a first end connected to its respective pressurized supply, a metering orifice portion, and a second end connected to an appropriate part of the engine. At least one of the metering orifice portions is adjustable for establishing various desired air-to-fuel ratios for delivery to the combustion cylinder. The system includes a pressure regulating apparatus in at least one of the lines, between its first end and its metering orifice portion for maintaining substantially equal pressures at all times in the respective supply lines immediately upstream of their respective metering portions. The respective supply line pressures immediately downstream of the metering orifices are also kept substantially equal by connection of both supply lines to a common conduit or mixing chamber.

Preferably a pressure regulating valve of the airloaded or dome-loaded type, which has a controlling pressure chamber and operates in response to changes in fluid pressure in such control chamber, is located in one line and has its control chamber connected to a sensing means so the chamber pressure has a predetermined relationship at all times to the pressure in the other supply line. A temperature control device may also be used in one or both lines to prevent undesired variations in air or fuel gas temperatures which could adversely affect the uniformity of the combustible mixture at different times during operation.

15 Claims, 2 Drawing Figures l l llglgluu PATENTEUHAR271973 NmN VM N INVENTOR.

Anton Braun 4770AJEV INTERNAL COMBUSTION ENGINE FUEL SUPPLY APPARATUS BACKGROUND OF THE INVENTION Internal combustion engines of both spark ignition and compression ignition types are well known. In some of these engines, fuel is supplied to a carburetor, which then mixes the desired proportions of fuel and air and delivers them to a combustion cylinder of the engine for normal starting and operation. I have previously suggested that the starting of internal combustion engines, and particularly free piston engines, can be facilitated by supplying an auxiliary starting mixture in which, in some cases, a different air-to-fuel ratio may be desirable during starting of the engine. Where such an engine is connected to an air compressor, or where a source of compressed air is otherwise available, the air for such a fuel air mixture has been supplied under pressure from one supply source, and the fuel, for example, a gaseous fuel such as methane or propane, has also been supplied under pressure from a separate source, such as a compressed fuel gas tank.

When air and fuel supply lines from such pressurized sources are connected through one or more suitable metering orifice portions to provide the desired air-tofuel ratio in a starting mixture, however, there have been problems in obtaining satisfactory starting of the engine, even though the respective metering orifices have been adjusted to provide what would normally be expected to be a suitable starting air-to-fuel ratio for the mixture. One important problem involves the provision of a proper mixture on the very first stroke of the engine. Another problem arises from the fact that in some engines, while an air-fuel mixture is being supplied, the pressures in the supply system are being varied substantially from moment to moment as the supply lines are opened and closed, e.g. by action of the engine piston in opening and closing an inlet port or by opening and closing of a control valve in the supply lines. When such ports or valves are closed, the pressure in the downstream portion of the supply line suddenly increases to the full supply line pressure and the flow is reduced to zero. When the port or valve opens, there is a sudden release of pressure at the downstream portion of the supply line and a resulting sudden change to a rapid flow condition.

SUMMARY OF THE INVENTION According to the present invention, I have found that the lack of uniformity in the operating results with a pressurized fuel and air supply system may be minimized or avoided by the provision ofan improved system for supplying a combustible air and fuel mixture, in which respective air supply and fuel gas supply lines each has a first end connected to an appropriate pressurized supply, and a metering orifice portion, at least one of which is adjustable for establishing various desired air-to-fuel ratios, and in which a pressure regulating apparatus is connected to at least one of the air and gas supply lines between its first end and its metering orifice portion for maintaining substantially equal pressures at all times in the respective supply lines immediately upstream of their respective metering orifice portions. Specifically, a variable pressure regulator in one line is controlled by pressure sensing means in the other line. The respective supply line pressures im- 0 changes in the fluid pressure in such control chamber,

is located in one of the lines and has its control chamber connected in such a manner that the pressure in the control chamber has a predetermined relationship at all times to the pressure in said one supply line immediately upstream of the orifice in that line, while the source of controlling pressure has a corresponding predetermined relationship at all times to the pressure immediately upstream of the orifice in the other supply line. Since the volume rate of air flow is normally much greater than the gas flow in air-fuel mixtures, the supply requirements placed by such a system on the air supply are greater and more severe than those placed on the gas supply. For this reason, and for greater sensitivity and reliability of control, such a pressure regulating valve is preferably located in the gas supply line and may have its control chamber connected directly to a point in the air supply line which is located between the metering orifice portion of that line and the pressurized air supply. In many cases it is also necessary or preferable to have a suitable constant pressure regulator located in whichever supply line is being used as the controlling pressure source, for example in the air supply line, at a point upstream from thepoint at which the control chamber of the pressure regulating valve for the other line, for example the gas supply line, is connected. Such a regulator can thus maintain a more nearly constant pressure upstream from the metering orifice 'portion of the line in which the pressure is sensed or used as the control pressure, which is at all times slightly lower than the pressure which is available just' upstream of the regulating valve in the other supply line. 7

Thus the regulating system just described maintains a pressure in the fuel gas supply line immediately upstream of its metering orifice portion which is substantially equal at all times to the pressure in the air supply line immediately upstream of its metering orifice. Since the other ends of the gas and air supply lines are connected to provide a common pressure, i.e. equal pressures at all times in the respective supply lines immediately downstream of their metering orifices, the pressure ratios across such orifices will be kept equal to each other (although substantially varying in actual value from moment to moment), despite substantial fluctuations in the common downstream pressure in said supply lines between the respective metering orifice portions and the engine, and despite substantial fluctuations in the pressures upstream of the metering orifice portions.

A temperature control device is also preferably used in one or both lines to prevent undesired variations in air or fuel gas temperatures which could adversely affect the uniformity of the combustible mixture at dif' ferent times during operation.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings which form a part of the application,

and in which like reference characters indicate like parts,

FIG. 1 is a schematic diagram showing an improved ,manner in which the improved fuel mixture control system of the present invention may be incorporated'in such an engine to provide an auxiliary combustible fuel mixture for starting the engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown schematically in FIG. 1, one embodiment of the invention is illustrated in connection with an internal combustion engine 201 which includes the usual combustion cylinder 202 with a power piston 203 connected to a suitable load, for example, by a crank shaft 204. A spark plug 206 may be used for ignition, when spark ignition is desired either for starting or running operation. An inlet port 207 in cylinder 202 may be connected to a suitable mixing, scavenging or other chamber 211. p

In some cases, it is desirable to provide a combustible starting or running mixture from a compressed air supply and compressed fuel gas supply, for example to provide a special auxiliary starting fuel mixture for the initial combustion stroke or strokes of such an engine. According to the present invention, such a fuel supply system includes respective air and fuel gas supply lines 216 and 217, each of which is connected to its respective compressed air or gas supply. Thus a first end 218 of the air supply line is connected to an air supply 98. This supply may either be a tank or receiver of compressed air, or a regular compressed air supply line in a commercial plant. Such a supply source provides compressed air as needed.

Similarly, the fuel gas supply line 217 has its first end 221 connected to a pressurized fuel gas supply 104. Such a supply may consist of either a pressurized fuel gas supply line in a commercial plant, or a pressurized fuel tank, for example, of methane or propane.

The second ends of air supply line 216 and fuel gas supply line 217 are connected to the engine in a manner to provide suitable mixing of the air and fuel. For this purpose, the lines 216 and 217 are connected to each other and to a common line or mixing chamber 213 at point 219. Chamber 213 may consist of a separate section of tubing or may actually be a mixing chamber in the inlet section of a suitable control valve 94 which controls the delivery of the desired combustible mixture, to the engine through conduit 212.

Each of the supply lines 216 and 217 has a metering orifice portion indicated at 222 and 223 respectively. At least one of these orifices is adjustable, as shown at 223, in order that the desired ratio of air-to-fuel may be obtained.

I have found, however, that a system including only the respective compressed air and compressed fuel gas supplies and the desired metering orifices does not always deliver the expected air-to-fuel ratio to the engine. The flow through lines 216 and 217 is interrupted, for example, when the valve 94 or inlet port 207 is closed. Conversely, when the inlet port 207 and valve 94 are open, there may be a sudden high volume rate of flow to the cylinder from each of the lines 216 and 217. l have found that these variations and interruptions resulted in delivery of nonuniform mixtures to the engine.

According to this invention, such undesired variations in the air-to-fuel ratio can be avoided or minimized by the provision of pressure control apparatus in at least one of these supply lines, in such a manner as to maintain substantially equal pressures in W each of the lines immediately upstream of the respective metering orifice portions 222 and 223. In the system shown in FIG. 1, a pressureregulating valve 226 is located in the gas supply line 217 just upstream from metering orifice portion 223, and is connected to a sensing means responsive to air line pressures upstream from 222. Regulator 226 is of the well-known type, sometimes referred to as an air-loaded or dome-loaded regulator, which includes a control chamber in which a suitable control pressure is varied in order to control the opening and closing of theinain valve of the regulator and thus control the pressure in line 217 between valve 226 and orifice 223. The pressure in the control chamber of regulator 226 is controlled by a line 227 connected to a source of control pressure in such a manner that the pressure in the control chamber of valve 226 will always bear a definite predetermined relationship to the instantaneous pressure in the supply line 216 immediately upstream of orifice 222, which corresponds to the predetermined relationship between the control pressure in valve 226 and the pressure in line 217 immediately upstream of orifice 223, thus maintaining the desired equality of instantaneous pressures immediately upstream of both orifices.

In this case the pressure control line 227 for the chamber or dome of regulator 226 is connected at a point 228 in the supply line 216 which is sufficiently close to the metering orifice portion 222 in that line.

Thus the supply line at 228 is the direct source of control pressure. By appropriate adjustment of pressure regulating valve 226 and by location of that valve sufficiently close to the metering orifice 223 in line 217, the instantaneous pressures in lines 216 and 217 immediately upstream from the respective orifices 222 and 223 can thus be kept substantially equal. Moreover, the merging of lines 216 and 217 at 219 in mixing conduit or chamber 213 in or upstream of the valve 94 provides a common or equal instantaneous pressure in each of lines 216 and 217 immediately downstream from the respective orifices 222 and 223. Thus, according to the invention, the instantaneous pressure differential or pressure ratio across metering orifice 223 is always kept substantially equal to the instantaneous pressure differential or pressure ratio across metering orifice 222, even though the actual pressure drops across both metering orifices may substantially increase or decrease simultaneously during the starting or running of the engine. If the upstream pressures were not regulated in such a manner as to maintain them substantially equal ahead of the metering orifices, than a change in the rate of flow, for example a sudden surge through the line 212 in response to opening of valve 94 and suction within the engine 201, could result in different instantaneous pressure differentials across the respective metering orifices, and a resulting variation in the intended flow rates for which these orifices were originally adjusted. In such a case the composition of the air-fuel mixture may vary considerably from the desired ratio. Thus the initial air-fuel mixture which might reach the engine when valve 94 is first opened could have a substantially different composition than the mixture which subsequently reaches the engine, and these variations in relative air-to-fuel ratios from moment to moment, depending on the variations of the instantaneous pressure ratios across orifices 222 and 223 could result in difficult starting or in misfires during operation or in other problems.

The provision of a pressure regulating system which maintains essentially equal pressures in the respective air and fuel supply lines immediately upstream of the orifices 222 and 223 from moment to moment during operation of the system has been found to avoid or minimize such problems and to insure smoother starting or running operation of the engine.

The pressure control system according to the invention further includes the provision of pressure regulating valves or other means to be sure that the pressure in whichever line is used as the controlling line (in this case the air supply line 216) is at all times lower than the pressure in the other supply line (in this case the fuel gas supply line 217). For this purpose a pressure regulating valve 229 of the pressure reducing type is located in line 216 between the first end 218 of the line and the point 228 at which the pressure is used to control the regulator 226 in line 217. If the normal pressure of the air supply 98 is substantially higher than the desired pressure at point 228, then an additional reducing valve 230 may also be employed in this same portion of the line 216. The pressure of the air supply from a compressor tank or recei er may range as high as 120 psig (pounds per square inch gauge). On the other hand, the compressed air line in a commercial plant may well have a substantially lower pressure, for example, of the order of psig. Similarly the fuel gas supply 104 could conceivably be of different types. In some cases, there may be a fuel gas supply line in a commercial plant where the gas pressure is of the order of only 3 psigor less. On the other hand, when the gas supply is taken from a gas tank, such as propane or methane, the pressure within the tank may be as high as 1,000 to 4,000 psig.

As shown in FIG. 1, the two reducing valves 229 and 230 are designed to provide a substantial pressure drop from an air supply which may be at the higher pressure range, in order to provide a pressure which is at least slightly lower at the point 228 upstream of orifice 222, than the gas supply pressure upstream of regulator 226. In this same system a reducing valve 232 may also be incorporated in the fuel gas supply line 217 between the pressure regulating valve 226 and the first end 221 of that line, especially when the fuel gas supply pressure at 104 is high. The combination of the particular pressure in the supply 104 and the particular adjustment of reducing valve 232 is designed to provide a pressure between the reducing valve 232 and the regulating valve 226 which is somewhat higher than the sure in line 216 immediately upstream from orifice 222.

As shown in FIG. 1, the air and fuel gas supply lines 216 and 217 also include respective one-way check valves 233 and 234 which permit flow from the supplies 98 and 104 toward the engine 201, but do not permit reverse flow in either line. These check valves are preferably located as shown, i.e., check valve 233 is positioned upstream from control point 228 and between that point and the pressure reducing regulator valve 229. Similarly check valve 234 is located in line 217 upstream of the pressure regulating valve 226 and between that valve and the reducing regulator 232.

In those cases where there is likely to be a substantial variation in the temperature at which either the air or fuel gas is supplied to the system of FIG. 1, the present invention also provides a suitable temperature regulating device, which is shown schematically at 233. Such a heat exchanger may be used between the respective air and fuel supply lines in order to bring both the air and fuel gas closer to a common temperature, in those cases where there is any substantial variance. This common temperature may conceivably go up or down from time to time during operation, but the maintenance of substantially common instantaneous temperatures helps insure the maintenance of the desired constant air-tofuel ratio at the engine.

In those cases where the temperature of either theair or fuel gas supply line is essentially fixed, then some form of cooling could be used only on the more variable of the two lines. For example, where the air supply 98 is from the receiving tank of a compressor, its temperature during operation mayconceivably rise substantially, e.g., to 500 Fahrenheit. In such a case, atmospheric cooling could be used on the air supply line at 218, without applying any temperature control to a substantially constant temperature gas supply line. On the other hand, if the air supply line 98 is in a plant where the lines remain at substantially constant temperature, and if the fuel gas supply 104 is from a liquid propane tank, where the pressures may vary over a range from 2,000 psig to 50 psig, then there .Could be a substantial difference in the gas temperature supplied at 221, and appropriate cooling or heating could be applied only to the gas line.

A preferred embodiment of the invention is shown in FIG. 2 in connection with the starting system of a free piston engine which is directly connected to drive a compressor, and which uses the receiving tank of the compressor as the supply source for compressed air for the auxiliary starting mixture supply system. As shown in FIG. 2, a free piston engine 17 has a power section 18 located at the extreme left of the engine and has a power. piston 20 reciprocating along the longitudinal central axis of the engine within a power cylinder 21. The housing of engine 17 is shown at 22. The engine is provided with respective inlet arid exhaust ports 14 and 16 in the wall of cylinder 21.

An outwardly-compressing compressor 23 is shown at the right end of engine 17. A shaft 24 interconnects power piston and a compressor piston 26. Compressor piston 26 is reciprocally movable along the central longitudinal axis of engine 17 within a compressor cylinder 28. Intake and discharge valves 30 and 32, respectively, are positioned at the right end of cylinder 28 to provide for the intake and discharge of fluid to and from a compressor chamber 34 formed between the right face 36 of compressor piston 26 and the inner face of end wall 38.

A bouncer control valve 37 provides for the control of pressure in a chamber 42 formed between the left face 44 of piston 26 and inner wall 48. Valve 37 provides for the control of fluid pressure in chamber 42 and allows chamber 42 to operate as a negative bounce chamber, i.e., a chamber in which compression of fluid during a leftward compression stroke of power piston 20 provides additional energy for a power stroke to the right, and in which the expansion of volume in chamber 42 during a power stroke to the right provides a reduced pressure or partial vacuum in chamber 42 to control the return stroke of pistons 20 and 26 to the left.

A bouncer valve spring 40, which is adjustable as shown schematically at 46, can be set to establish a suitable maximum pressure within bounce chamber 42. Higher pressures will then be vented through conduit 87, valve 37 and outlet 88.

The engine will also include other known features, the details of which are not essential to an understanding of the present invention.

During operation, the output from compressor chamber 34 is fed through one-way valve 32 into a compressor discharge manifold 52. The discharge manifold has an outlet conduit 53 which communicates with a further conduit 54 connected to a suitable receiver, i.e., air storage tank or reservoir 56. Communication between conduits 53 and 54 is controlled by a spring loaded discharge valve 57 which has a loading spring 58 normally urging valve 57 to closed position. When the engine starts operation and sufficient pressure is generated within conduit 53 to overcome the resistance of spring 58, valve 57 can snap to a fully open position to provide complete communication fromconduit 53 to conduit 54. Thus, the output from the compressor will be fed to the storage reservoir 56.

In order to relieve the pressure within compressor chamber 34 whenever the engine shuts down, and thus facilitate starting the engine, a manifold pressure discharge conduit 59 is connected at one end to discharge manifold 52. The other end of conduit 59 is controlled by a valve 61 which is shown in H6. 2 in its normal operating position in which conduit 59 is closed. Upward movement of the movable control portion of the valve against the urging of spring 62, effectively connects conduit 59 with a further conduit 63 by means of valve passage 64. Conduit 63 is connected to the chamber 65 providing a desired back-pressure on the rear side of valve 57. Thus when valve passage 64 is moved into upper operating position, the pressure within manifold 52, which is already applied to the upper or front side of valve member 57, will be applied through conduits 59 and 63 to the rear side of valve 57. With equal pressure on each side of valve 57, the spring member 58 will immediately become effective to force the valve to closed position. The pressure within manifold 52, conduits 59 and 63 and chamber 64 will .then gradually be relieved, while valve passage 64 is in its upper position, through a suitable bleed orifice, shown schematically at 66, which communicates with conduit 63 between valve 61 and chamber 65.

Valve 61 is operated in any suitable manner at the time the engine is shut down, in order to insure closing of outlet valve 57 and thus prevent escape of pressure from receiving reservoir 56 back through the manifold 52. In effect, valve 57 and its associated controls provides a one-way check valve for the output from manifold 52. This check valve has a positive action in both directions between a fully open position in which it accomodates the full output of compressor chamber 34, and a fully closed position which effectively retains the pressure in receiver 56.

Valve 61 may be connected to main ignition switch 67, for example, so that the valve is moved from the running position of FIG. 2 to its upper bleed position, with passage 64 connecting conduits S9 and 63, whenever niain switch 67 is opened to turn off the ignition. Switch 67 may be opened manually, or in response to predetermined pressure build-up in reservoir 56, or in some other suitable manner.

For a desired starting cycle, a three-position valve 68 is provided which may be axially movable from one position to another and which is normally held in the position shown in FIG. 1 by equal and opposed spring means 69 and 70. In this normal running position, the central section 72 of valve 68 blocks communication between the conduits to be described below, which are used only for positioning the piston assembly prior to and during the starting operation. One incoming valve conduit 73 is connected by valves shown schematically at 74 and 76 to the pressure receiver or reservoir 56, or to a suitable source of auxiliary pressure, which need not have the high pressure which is ordinarily found in a storage reservoir such as 56. A reducing valve 77 is used in conduit 73 to provide the desired reduced pressure for the starting mechanism and also, as described below, for the compressed air supply line of the starting mixture supply system of the present invention.

Another conduit 78 on the same side of valve 68 as conduit 73 is connected so that it is open to atmosphere for relief of desired pressures as described below.

Valve 68 includes additional valve sections79 and 81 which provide cross connections between the respective conduits 73 and 78 at one side of the valve, and conduits 82 and 83 at the other side of the valve 68. Conduit 82 is connected at 84 to the compressor chamber 34. Conduit 83 is connected at 86 to a conduit 87 connecting the bouncer chamber 42 with valve 37 and bouncer outlet 88.

In operation, when engine 17 is shut down and it is desired to position the pistons 20 and 26 for a starting cycle, valve 68 is first operated to the right so that vaive section 79 connects conduit 73 with bouncer conduit 83 and thus introduces air under pressure from reservoir 56 and regulator 77 into the conduit 87 and bouncer chamber 42. At the same time, the valve section 79 also connects conduit 82 to exhaust conduit 78. Thus the compressor chamber 34 is effectively connected by a completely open connection to the atmosphere to relieve any pressure in that chamber. The resulting difference of pressure between the relatively higher pressure in bouncer chamber 42 and the ambient or atmospheric pressure in compressor chamber 34 forces compressor piston 26 and associated parts to the right toward the outer end of compressor cylinder 28.

If valve 68 is now permitted to return at least momentarily to its normal position as shown in FIG. 2, the compressor piston and associated parts will remain in their right hand position for starting.

The starting is achieved by feeding an auxiliary starting mixture of combustible gas and air into the power cylinder 21 and then igniting it by a spark at spark plug 89.

A carburetor or mixer 91 is shown in block diagram and is connected in normal fashion at 92 to a regular gas supply 93. Thus, during normal running of the engine, the carburetor and gas supply will deliver the desired gas to the power cylinder 21 at the proper times when inlet 14 is opened on an outward movement of piston 20 at the end of a power stroke to the right.

A special starting valve means 94 is provided with two valve sections 96 and 97. When valve section 96 is in position as shown in FIG. 2 during normal running of the engine, nothing passes through valve 94.

When the valve is operated to the left, however, it connects the auxiliary air and gas supply system to the cylinder 21 through mixer 91. In this case the air supply line is shown at 99 and the fuel gas supply line at 106. These lines are connected to the respective air supply line 98 and auxiliary fuel gas supply tank 104 by a pressure regulating apparatus which operates in the same manner described in connection with FIG. 1. The air supply 98 in this case consists of a line connected to the pressure reducer 77 and in turn to the receiver or pressure tank 56 of the compressor. Since the air temperatures in a compressor in this sort of free piston engine compressor system tend to rise during operation to as much as 540F., a heat exchanger 238 is positioned in the air supply line 99 as shown in FIG. 2. A suitable cooling medium is fed into the exchanger 234 at 239 and exhausted at 241. The cooling medium may be from a separate source or may even be a line (not shown) from the auxiliary gas supply 104. A pressure regulating valve 229, as in FIG. 1, provides the desired further reduction of pressure for the air supply line and provides a more even pressure output through check valve 233 to point 228 upstream from the metering orifice portion 222 of line 99. Similarly, from the auxiliary gas supply 104, the fuel gas is fed through a constant pressure reducing regulator 232, through check valve 234, to pressure regulating valve 226, and,then to the fuel gas metering orifice 223. Regulator 226 has its control line 227 connected at 228 to the air supply line in the same manner and for the same purpose as described in connection with FIG. 1.

When valve 94 is operated to the left, air supply line 99 is connected to valve conduit 101 leading to the carburetor 91 by valve passage 102 in valve section 97. Valve section 97 also includes another passage 103 for connection of the gas supply line 106 to conduit 107 and mixer 91.

Thus, operation of starter valve 94 to the left is designed to introduce into the power cylinder 21 the appropriate combustible starting mixture of gas and air, as needed during the starting cycle. It might be noted at this point that the auxiliary air is particularly necessary to provide a combustible mixture on the initial starting strokes in those cases where the free piston engine normally operates with air supplied to the power cylinder or to the mixer by a suitable scavenge system. Such a system is shown schematically in FIG. 2 with reference to the chamber 107 between power piston 20 and inner wall 49. An inlet valve 108 permits air to enter chamber 107 when the power piston 20 is moving to the left. Then, when .the power piston 20 returns to the right, for example during a power stroke, outlet valve 109 connects the scavenge chamber 107 either directly with intake 14 or with mixer 91, depending on the type of engine arrangement involved. Thus, during normal operation of the engine, the movement of power piston 20 with respect to scavenge chamber 107 will provide a sufficient flow of air to properly charge the power cylinder.

Since, however, such a scavenge system provides no air output when piston 20 is at rest prior to a start, starter valve 94 and the auxiliary air and fuel gas supply system provide the necessary mixture of air and fuel gas to achieve a combustible mixture in the power cylinder for the starting operation.

Thus, a starting cycle for the device of FIG. 2 requires operation of starter valve 94 from the position of FIG. 1 to its left position in which section 97 of valve 94 becomes operative to connect the auxiliary air and gas supply lines. At the same time, valve 68 (which has previously been operated to its right-hand position) should now be operated to the left, so that valve section 81 will connect the low pressure air from conduit 73 through conduit 82 to the compressor chamber 34 and vent bouncer chamber 42 to the atmosphere at 78.

Thus, the higher pressure in chamber 34 starts movement of compressor piston 26, shaft 24 and power piston 20 to the left in a manner corresponding to its movement during a regular compression stroke.

As the pistons move to the left, power piston 20 will first move past the outer end of inlet port 14 and then gradually close this port, as well as exhaust port 16. As soon as the intake and exhaust ports 14 and 16 are substantially closed, or shortly thereafter, the ignition system is operated to provide a spark at 89 to ignite the combustible mixture in power cylinder 21 and provide a first combustion or power stroke of piston 20 to the right. The spark for this initial combustion is provided by a position-responsive actuator, i.e., an arrangement in which ignition is triggered at a specific position of the power piston 20 and associated parts along the path of movement of the piston. Thus a set of breaker points 112 is supported on an adjustable slide 113, which is movable axially of the engine within a guide slot 114. A manual adjusting knob 116 extends outwardly of the casing to permit adjustment of the position at which the contacts will be actuated initially.

As is customary in the art, one of the breaker points 112 is carried on a movable supporting arm 117, and the other is on a relatively stationary arm 118. An intermediate spring 119 normally urges the points apart from each other, and a stop 121 limits the upward movement of the movable contact arm 1 17. This movable arm carries an actuating portion designed for engagement by a timing cam 122, suitably mounted on a support 123 carried by the piston shaft 24, or by some other suitable portion of the engine which moves in synchronism with the power piston 20. The movable contact is connected in known manner by a suitable wire 124 to the positive side of the battery 127, the negative side of which is grounded at 128. Another wire 129 connects the fixed contact through main switch 67, with the primary winding 131 of ignition coil 132. The secondary winding 133 of ignition coil 132 is' connected to the spark plug 89, and the respective ignition coil windings 131 and 133 are grounded, as shown, to complete the normal circuit.

In FIG. 2, the power piston is shown at the outer dead point or reversal point of its path with the power face of the piston at the location indicated by the arrow and dotted line 137. During normal operation it is desirable that the piston move to the left during a compression stroke, until it reaches a normal inner reversal point indicated by the dotted arrow 138.

As power piston 20 moves from position 137 toward position 138 and the power cylinder 21 is filled with a suitable combustible mixture through operation of valve 94, the timing position adjustment at 116 is set initially, so that the breaker points will be actuated by cam 122 as the inner power piston face reaches the intermediate point 139 along its path, i.e., some time after the intake and exhaust valve ports have been substantially closed, but without necessarily waiting until the piston completely reaches its inner reversal point 138. At this point 139, the combustible mixture in 21 will be under substantially less pressure than the compression ratios which would be customary in regular running of the engine with afull compression stroke. The starting movement of piston 20 from right to left, as already described, is under only the pressure fed by valve 68 to chamber 34. Since the area of piston 26 is generally greater than that of power piston 20, a given pressure in chamber 34 can produce a somewhat higher pressure in the power cylinder, but requires no particular pressure therein.

in any event, the ignition contacts are set by adjusting member 116 to produce the initial combustion for a first power stroke of the power piston 20 at a point which will surely be reached as the piston moves from right to left, without necessarily waiting for the piston to move farther to the left than the intermediate point 139. This initial low compression power stroke will ordinarily provide less work than a normal later power stroke after the engine has been started, but it will be sufficient to start the reciprocation of the pistons. Ignition adjustment member 116 may then gradually be moved to the left, so that successive power strokes are started by combustion at points gradually closer to the normal desired inner reversal point 138. After the initial combustion stroke, the movement of power piston 20 will also start operation of the normal scavenge air system through chamber 107 and valve 109, so that subsequent combustion can be achieved in more normal manner by the regular supply of gas through mixer 91 and air from the scavenge system. Thus valve 94 can then be operated back to its right-hand position to cut off the auxiliary gas and air supply system of the present invention.

Although the improved air-fuel mixture supply system according to the present invention is particularly useful in connection with an auxiliary starting system for an internal combustion engine, it is also suitable for possible application as the main supply system for normal running of an engine in those cases where there is a desire or need to operate such an engine from respective compressed air and fuel gas suppliesv Also, although the system has been illustrated with the use of an air-loaded or air-controlled pressure regulating valve in one line, which is responsive to the instantaneous pressures in the other line, it will beunderstood that other pressure control devices can be used according to the invention. For example, a pressure transducer in one line which provides a suitable electrical signal could be used to control electrically a pressure regulator in the other line. Also fluidic control elements may be used for the desired control functions.

The term pressure, as used in connection with the pressures in the respective supply lines immediately upstream and downstream from their metering orifice portions, is used in this application to mean total pressure, i.e., a pressure which includes both the static pressure and any appreciable velocity components. Also, the references to a fuel gas supply, such as a tank of methane or propane, are not intended to exclude a system in which, in place of such a fuel gas, the gas supply line receives a mixture of air and at least partially atomized or vaporized liquid fuel, e.g. an overrich air-fuel mixture.

Moreover, although the specific embodiments of FIGS. 1 and 2 involve a coupling between a pressure regulator in one line and a pressure sensing means or source of control pressure in the other line, the present invention is not limited to the use of such a coupling, but includes the use of any other means capable of functioning to maintain substantially equal pressures in the two supply lines immediately upstream of their respective metering orifice portions,in combination with means for maintaining substantially equal pressures in both supply lines immediately downstream of their respective metering orifice portions, despite possible substantial variations from moment to moment in the actual pressures immediately downstream and/or upstream of said orifice portions.

The primary requirement is that whatever system is used should maintain substantially equal instantaneous pressures in the respective air and fuel gas supply lines at points immediately upstream of the metering orifices in such lines and that the pressuredrop from moment to moment across the respective metering orifices shall be maintained as nearly equal as possible. Some tuning of such a system may be required in order to achieve optimum operation, and it will be understood that the sizes of the lines, the configuration of the lines, the relative location and arrangement of the various regulators, and/or other factors can be varied widely by persons skilled in the art without departure from the principles described above. These principles have been described in the foregoing specification together with some of the ways in which the invention can be practiced.

I claim:

1. In an internal combustion engine having a cylinder, the improvement comprising a pressurized supply system through which a combustible mixture may be supplied to said engine, said supply system comprising a compressed air supply line having a first end thereof for connection to a compressed air supply from which air is supplied to the line, a compressed fuel gas supply line having a first end thereof for connection to a pressurized fuel gas supply from which fuel gas, such as propane and methane, is supplied to such line, a first metering orifice portion in said air supply line, a second metering orifice portion in said fuel gas supply line, means for adjusting at least one of said first and second metering orifice portions for establishing a desired air-to-fuel ratio at which said supply lines respectively deliver air and fuel to said engine, means providing a mixing chamber, each of 'said air and gas supply lines being connected to said mixing chamber downstream from said metering orifice portions and thereby maintaining substantially equal pressures in said supply lines immediately downstream of their respective metering orifice portions, and pressure regulating apparatus connected to at least one of said air and gas supply lines between its first end and its metering orifice portion for maintaining substantially equal pressures at all times in the respective supply lines immediately upstream of their respective metering orifice portions.

2. An internal combustion engine according to claim 1 in which the pressure regulating apparatus includes a variable pressure regulating valve located upstream from the metering orifice portion in one of said supply lines, a pressure sensing means responsive to instantaneous pressures in the other supply line at a point upstream from the metering orifice portion of said other supply line, and means interconnecting the pressure regulating valve and pressure sensing means and thereby operating the regulating valve and varying the pressure in said one supply line in response to changes in pressure in said other supply line.

3. An internal combustion engine according to claim 2 in which said pressurized supply system is an auxiliary starting mixture supply system which delivers a combustible starting mixture to said engine.

4. An internal combustion engine according to claim 3 in which the variable pressure regulating valve is located in the fuel gas supply line and the sensing means is located in the air supply line.

5. An internal combustion engine according to claim 3 in which said supply system includes valve means positioned downstream of the respective metering orifice portions for selectively closing and opening the air and fuel gas supply lines.

6. An internal combustion engine according to claim 3 in which the pressure regulating valve has a control pressure chamber connected to a source of fluid control pressure and varies the pressure in said one supply line in response to variations in the fluid control pressure within the control chamber, and the pressure sensing means provides a source of fluid control pressure which has a predetermined relationship at all times to the pressure in the other supply line immediately upstream of its metering orifice portion, the pressure in said control chamber having a corresponding predetermined relationship at all times to the pressure in said one supply line immediately upstream of its metering orifice portion.

7. Internal combustion engine starting apparatus according to claim 6 in which the control chamber of the variable pressure regulating valve is connected directly to the other supply line and the pressure regulating valve constantly regulates the pressure in said one line in response to the pressure in the other line.

8. Apparatus according to claim 6 in which the pressure regulating valve is in the fuel gas supply line, and the source of fluid control pressure is a direct connection to the air supply line at a point upstream from the metering orifice portion of the air supply line.

9. An internal combustion engine according to claim 3 having temperature control means in at least one of the air and gas supply lines upstream of the respective variable pressure regulating valve and pressure sensing means.

10. An internal combustion engine according to claim 3 in which the engine is a free piston engine, said pressure regulating valve is an air-loaded pressure regulating valve in the gas supply line upstream from the orifice means in said line, the air-loaded regulating valve has a control pressure chamber, and the sensing means connects the control pressure chamber to the air supply line at a point upstream from the orifice means of the air supply line.

11. An interval combustion engine according to claim 10 in which the free piston engine is connected to an air compressor having an air receiving pressure reservoir, and the first end of the air supply line is connected to said compressor reservoir, the supply system including temperature control means connected to the air supply line, said temperature control means com prising means for controlling the temperature of the compressed air flowing from said reservoir through the air supply line.

12. An engine according to claim 10 in which the air supply line includes a manually adjustable constantoutput-pressure reducing regulator between the first end of the air supply line and the point to which the control pressure chamber of the variable pressure regulating valve in the gas supply line is connected.

13. An engine according to claim 12 in which the gas supply line includes a manually adjustable constantoutput-reducing regulator between the first end of the fuel supply line and the variable pressure regulating valve.

14. Apparatus according to claim 10 in which each of the air and fuel gas supply lines includes a one-way check valve, the air supply line check valve being positioned between the first end of the air supply line and the point at which the control chamber of the variable pressure regulating gas supply line valve is connected, and the fuel gas supply line check valve being positioned between the first end of the gas supply line and the variable pressure regulating valve.

15. In an internal combustion engine having a cylinder, the improvement comprising a pressurized supply system through which a combustible mixture may be supplied to said engine, said supply system comprising a compressed air supply line having a first end thereof for connection to a compressed air supply from which air is supplied to the line, a compressed fuel gas supply line having a first end thereof for connection to a pressurized fuel gas supply from which fuel gas, such as propane and methane, is supplied to such line, a first metering orifice portion in said air supply line, a second metering orifice portion in said fuel gas supply line, means for maintaining substantially equal pressures in said supply lines immediately downstream of 

1. In an internal combustion engine having a cylinder, the improvement comprising a pressurized supply system through which a combustible mixture may be supplied to said engine, said supply system comprising a compressed air supply line having a first end thereof for connection to a compressed air supply from which air is supplied to the line, a compressed fuel gas supply line having a first end thereof for connection to a pressurized fuel gas supply from which fuel gas, such as propane and methane, is supplied to such line, a first metering orifice portion in said air supply line, a second metering orifice portion in said fuel gas supply line, means for adjusting at least one of said first and second metering orifice portions for establishing a desired air-to-fuel ratio at which said supply lines respectively deliver air and fuel to said engine, means providing a mixing chamber, each of said air and gas supply lines being connected to said mixing chamber downstream from said metering orifice portions and thereby maintaining substantially equal pressures in said supply lines immediately downstream of their respective metering orifice portions, and pressure regulating apparatus connected to at least one of said air and gas supply lines between its first end and its metering orifice portion for maintaining substantially equal pressures at all times in the respective supply lines immediately upstream of their respective metering orifice portions.
 2. An internal combustion engine according to claim 1 in which the pressure regulating apparatus includes a variable pressure regulating valve located upstream from the metering orifice portion in one of said supply lines, a pressure sensing means responsive to instantaneous pressures in the other supply line at a point upsTream from the metering orifice portion of said other supply line, and means interconnecting the pressure regulating valve and pressure sensing means and thereby operating the regulating valve and varying the pressure in said one supply line in response to changes in pressure in said other supply line.
 3. An internal combustion engine according to claim 2 in which said pressurized supply system is an auxiliary starting mixture supply system which delivers a combustible starting mixture to said engine.
 4. An internal combustion engine according to claim 3 in which the variable pressure regulating valve is located in the fuel gas supply line and the sensing means is located in the air supply line.
 5. An internal combustion engine according to claim 3 in which said supply system includes valve means positioned downstream of the respective metering orifice portions for selectively closing and opening the air and fuel gas supply lines.
 6. An internal combustion engine according to claim 3 in which the pressure regulating valve has a control pressure chamber connected to a source of fluid control pressure and varies the pressure in said one supply line in response to variations in the fluid control pressure within the control chamber, and the pressure sensing means provides a source of fluid control pressure which has a predetermined relationship at all times to the pressure in the other supply line immediately upstream of its metering orifice portion, the pressure in said control chamber having a corresponding predetermined relationship at all times to the pressure in said one supply line immediately upstream of its metering orifice portion.
 7. Internal combustion engine starting apparatus according to claim 6 in which the control chamber of the variable pressure regulating valve is connected directly to the other supply line and the pressure regulating valve constantly regulates the pressure in said one line in response to the pressure in the other line.
 8. Apparatus according to claim 6 in which the pressure regulating valve is in the fuel gas supply line, and the source of fluid control pressure is a direct connection to the air supply line at a point upstream from the metering orifice portion of the air supply line.
 9. An internal combustion engine according to claim 3 having temperature control means in at least one of the air and gas supply lines upstream of the respective variable pressure regulating valve and pressure sensing means.
 10. An internal combustion engine according to claim 3 in which the engine is a free piston engine, said pressure regulating valve is an air-loaded pressure regulating valve in the gas supply line upstream from the orifice means in said line, the air-loaded regulating valve has a control pressure chamber, and the sensing means connects the control pressure chamber to the air supply line at a point upstream from the orifice means of the air supply line.
 11. An interval combustion engine according to claim 10 in which the free piston engine is connected to an air compressor having an air receiving pressure reservoir, and the first end of the air supply line is connected to said compressor reservoir, the supply system including temperature control means connected to the air supply line, said temperature control means comprising means for controlling the temperature of the compressed air flowing from said reservoir through the air supply line.
 12. An engine according to claim 10 in which the air supply line includes a manually adjustable constant-output-pressure reducing regulator between the first end of the air supply line and the point to which the control pressure chamber of the variable pressure regulating valve in the gas supply line is connected.
 13. An engine according to claim 12 in which the gas supply line includes a manually adjustable constant-output-reducing regulator between the first end of the fuel supply line and the variable pressure regulating valve.
 14. Apparatus according to claim 10 in whiCh each of the air and fuel gas supply lines includes a one-way check valve, the air supply line check valve being positioned between the first end of the air supply line and the point at which the control chamber of the variable pressure regulating gas supply line valve is connected, and the fuel gas supply line check valve being positioned between the first end of the gas supply line and the variable pressure regulating valve.
 15. In an internal combustion engine having a cylinder, the improvement comprising a pressurized supply system through which a combustible mixture may be supplied to said engine, said supply system comprising a compressed air supply line having a first end thereof for connection to a compressed air supply from which air is supplied to the line, a compressed fuel gas supply line having a first end thereof for connection to a pressurized fuel gas supply from which fuel gas, such as propane and methane, is supplied to such line, a first metering orifice portion in said air supply line, a second metering orifice portion in said fuel gas supply line, means for maintaining substantially equal pressures in said supply lines immediately downstream of their respective orifice portions, and means for maintaining substantially equal pressures in said supply lines immediately upstream of their respective orifice portions, despite possible variations from moment to moment in the actual pressures immediately downstream and upstream of said orifice portions. 